1. Field of the Invention
The invention relates to a sag (deflection) compensation roll with a rotatable roll jacket, a non-rotating carrier arranged inside the roll jacket, and a hydraulic support element arrangement between the carrier and the roll jacket. A bearing ring is located at each end of the roll jacket, which can be moved relative to the carrier in a press plane, and a beating arrangement is located between the bearing ring and the roll jacket.
The invention also relates to a process for operating a sag compensation roll with a roll jacket that rotates around a carrier and is supported in the area of each of its axial ends by a bearing arrangement that has a bearing ring and at least three hydrostatic support elements with bearing pockets distributed over the bearing ring in the circumferential direction.
2. Discussion of Background Information
Such a sag compensation roll is known from, e.g., EP 0 332 594 B1. In operation, the roll jacket rotates around the carrier. Sags that might result from a loading of the roll jacket are accepted by the hydraulic support element arrangement that supports the roll jacket from inside against the carrier. While this does lead to a sagging of the career under certain circumstances, the elastic line of the roll jacket can correspondingly be better influenced.
The support element arrangement, however, can only accept forces that act in the press plane, for example, that are produced by an opposing roll or an adjacent roll stack. It is also necessary for the roll jacket to be held on the carrier with a bearing that allows the roll jacket to rotate against the carrier and simultaneously allows a certain positioning.
This bearing or, more generally, this bearing arrangement, is loaded differently in different situations. In operation, the roll jacket is supported against the carrier by the hydrostatic support elements. Thus, the bearing arrangement can be held virtually free of support forces, at least with a vertically oriented roll stack, in which the support elements also produce a vertically oriented force component between the carrier and the roll jacket. The weight of the roll jacket itself and the forces acting in the press direction, which are applied by other rolls, are absorbed by the support elements between the roll jacket and the carrier. In this case, the bearing arrangement serves virtually exclusively to position the roll jacket against the carrier. When the nips of the roll stack are opened, the weight of the roll jacket rests on the bearing arrangement. In this case, the bearing arrangement must be capable of accepting this weight, even when the roll jacket rotates. In all cases, it must be ensured that the bearing arrangement runs with the smallest possible amount of play, which must not exceed a predetermined amount.
In the known case, this bearing is formed by a roll body, as is customary in the state of the art. It has been found, however, that such roll bearings no longer work with the necessary reliability when the rolls run ever faster.
The present invention provides a sag (deflection) compensation roll which is operable at a higher operating speed.
The sag compensation roll of the instant invention includes a bearing arrangement formed by at least three hydrostatic support elements which are distributed in the circumferential direction. At least one of the at least three hydrostatic support elements can move with respect to the bearing ring.
It is thus possible to operate a sag compensation roll with a jacket lift even at higher speeds, i.e., circumferential speeds on the order of magnitude of about 2000 m/min and above. The presence of at least three support elements distributed in the circumferential direction allows a defined supporting in all radial directions. Since at least one, but preferably several or even all, of the support elements can move against the bearing ring, they are capable of self-adjusting even when there are diameter changes of the roll jacket and/or the bearing ring or the carrier, which do not always need to run alike. Thus, they are able to guarantee that the roll jacket is always supported to the desired extent. Plays, as are known from roll bearings and that could lead under certain circumstances to an unfavorable oscillation behavior of the roll during operation, are kept very low with this type of bearing. In addition, the hydrostatic support of the roll jacket in the area of the rotation bearings enables relatively low-wear operation, even at higher speeds.
The fact that, in a preferred embodiment, the effective surface of the bearing pocket arrangement, i.e., the area in which the pressure can act between the roll jacket and the support element, is greater than the effective surface between the support element and the bearing ring, ensures that the support element can indeed be pressed into the bearing ring with a certain force when corresponding forces act on the roll jacket. Since hydraulic pressures build up above and below the support element, however, the force with which the support element lies against the bearing ring remains limited. Its magnitude can be influenced by the difference in area. This results in a stable support, even when the diameters of the roll jacket change. It is virtually always ensured that the roll jacket can slip on a film of fluid.
It is also preferred for the support element to be able to be driven into the bearing ring under load up to its fixed position. No relative movement that could lead to friction occurs between the foot surface of the support element and the bearing ring, so that it can certainly be accepted here that the support element can be driven into the bearing ring xe2x80x9cup to the stop.xe2x80x9d During operation, the roll jacket is supported in the known manner, e.g., by the support elements between the carrier and the roll jacket or else by further rolls arranged below the roll jacket, which rolls form a nip with the sag compensation roll in question. In this case, the bearing arrangement is virtually free of external support forces. It serves primarily to position the roll jacket against the carrier. Owing to the at least one movable support element between the bearing ring and the roll jacket, it is possible to design the bearing arrangement with a decidedly small amount of play. The support elements can be held always in the immediate vicinity of the inside of the roll jacket, with the formation of a fluid film of the hydraulic fluid.
It is also advantageous if the bearing pocket arrangement is connected with a supply device that delivers a constant volume flow of hydraulic fluid. Owing to the supplying of the bearing pockets with a constant volume flow of the hydraulic fluid, changes in loading can also be received without difficulty, Even when the weight of the roll jacket must be carried by the bearing arrangement, a reliable support is possible without difficulty. The support element lying against the direction of the force of gravity is thus driven into the bearing ring up to the stop, i.e., into its fixed position. The supplying of the bearing pockets with a constant volume flow of the hydraulic fluid, however, still ensures that the fluid film is maintained between the support element and the roll jacket, largely independently of the loading. A constant pressure difference prevails between the cylinder chamber below the support element and the hydrostatic pocket between the support element and the roll jacket, owing to the constant volume flow of hydraulic fluid. By applying load to the roll, the support element facing the nip is supported on the floor of its cylinder bore. Since its capillary continues to be supplied with hydraulic fluid, however, and at a constant volume flow, the pressure will rise in the pockets. At every load, the pressures in the pockets adjust automatically. By the constant volume flow, it is possible to ensure that the support function is maintained for each support element, independently of the load.
The bearing pocket arrangement is preferably connected to a pressure chamber between the support element and the bearing ring via a capillary arrangement traversing the support element. A drop in pressure that ensures that a certain gap is always present between the support surface of the support element adjacent to the roll jacket can be achieved via the capillary arrangement. Owing to the supply device that delivers a constant volume flow of hydraulic fluid, a constant pressure difference prevails between the cylinder chamber below the support element and the hydrostatic pocket between the support element and the roll jacket. By the application of load on the roll, the support element facing the nip is supported on the floor of its cylinder bore. Since its capillary continues to be supplied with hydraulic fluid, however, at a constant volume flow, the pressure in the pockets will rise. At every load, the pressures in the pockets adjust automatically. By the constant volume flow, it is possible to ensure that the support function is maintained for each support element independent of the load, even when the support element is inserted up to the stop.
The capillary arrangement is preferably dimensioned so that, in the unloaded state, a predetermined initial stressing force is not exceeded, and, at a predetermined loading, a predetermined minimum gap height is substantially guaranteed. The unloaded state is easy to ascertain. The capillary arrangement is dimensioned so that, in the unloaded state, an adequate amount of hydraulic fluid can flow to the bearing pocket arrangement, so that the pressure in the pressure chamber does not exceed a predetermined value. Thus, in the unloaded state, too strong a loading of the roll jacket is prevented. Vice versa, the throttle resistance of the capillary arrangement must not be too low, so that at every load it is guaranteed that the gap between the support element and the roll jacket is maintained at a predetermined order of magnitude.
Here, it is particularly preferred for the supply device to be matched to the capillary arrangement such that, at maximum load, a minimum gap in the range of about 20 to 30 xcexcm results between the support element and the roll jacket. This gap is sufficiently wide to prevent damage to the roll jacket by being placed on the support element. However, it is small enough for the support element to sufficiently throttle the oil flow, so that fluid consumption remains at a reasonable level.
It is advantageous for the movable support elements to have a lift height with respect to the bearing ring in the radial direction that corresponds to a maximum change resulting from thermal differences in diameter and/or roll jacket or carrier deformations arising from nip loads. Therefore, lift height will be limited to very small values. The lift must be only so great that the above-mentioned changes resulting from thermal differences in diameter and deformations of the roll jacket or the axles arising from nip loads can be compensated for. The jacket lift of the roll is performed by guiding the bearing ring on the carrier. Owing to the very small lift height, a relatively precise guiding is possible in the bearing ring over the entire working area of the support elements. This again improves the operating properties of the roll.
Here, it is particularly preferred for the lift height to be in the range of about 0.1 to 0.5 mm. This corresponds essentially to the play of a C3 self-aligning roller bearing, where it is guaranteed by the lift height that no play occurs with the support described.
Preferably, at least one support element has a curved floor on its underside facing the carrier. This holds true in any case for the support element that is pressed further into the bearing ring when there is a pressure impact on the roll jacket in the press plane. The curved floor prevents the support element from being placed with an edge on the floor of the cylinder bore when the carrier is curved by loading. This reduces wear. A hydrostatic bearing for a roll with a jacket lift is made available that meets the requirements of a bending carrier relatively well. The curved floor of the support element can either sit directly on the floor of the cylinder bore and xe2x80x9croll offxe2x80x9d there when the carrier is curved by loading. It is also possible, however, to arrange a ring or another correspondingly concave support surface on the floor of the cylinder bore, on which the support element lies. In this case, the support element continues to be supported flat on the floor of the cylinder bore and can nevertheless incline.
In an alternative embodiment, it is provided that at least one support element is arranged in a cylinder housing and has a concave floor supported on the carrier on a correspondingly shaped convex surface. In this case as well, it is permissible for the carrier to sag. Here, however, the support element remains aligned with the cylinder bore in the cylinder housing. The complete cylinder housing can then be displaced on the arched surface. A full-surface support is maintained here as well.
Preferably, the support elements at one end of the roll have a curved support surface lying against a similarly curved bearing surface on the inside of the roll jacket. With this embodiment, an axial bearing of the roll jacket with respect to the bearing ring is achieved on one side in a relatively simple manner. Owing to the curvature of the bearing surface, the roll jacket cannot be displaced axially against the support element.
Here, it is particularly preferred for the support surface to be curved in a circular line resulting in a radial section. With this embodiment, in addition to the axial supporting, the effect is also achieved that the carrier can sag with respect to the roll jacket without the support properties of the support elements being impaired to a significant extent. When the carrier sags, the support surface travels with its surface along this circular line, but continues to support the roll jacket reliably.
In an alternative or additional embodiment, it can be provided that a bearing ring lies against the roll jacket axially via hydrostatic slip surfaces. In this manner, a fixed bearing can be implemented at one axial end of the roll.
Preferably, the bearing rings are arranged on end sections of the carrier that have a smaller diameter than a section of the carrier axially between the end sections. Two advantages are gained thereby. In particular, there is enough space available that can be used to accommodate the bearing rings and the support elements. Moreover, the carrier is dimensioned sufficiently amply in the middle range over the greatest part of its length to be able to support the hydraulic support element arrangement. This again has the result that the sagging of the carrier and thus also the inclination of the support elements to the roll jacket can be kept small.
A spring is preferably arranged between the bearing ring and the support element. As explained above, the support elements are acted upon with a constant volume flow that also reaches the bearing pockets. The support elements have only a small lift in the bearing ring, corresponding approximately to the bearing play of a roll bearing. In the case of a pending bearing force, the loaded support elements are driven into the bearing ring to the stop or into their fixed position. In this case, the pressure over the support element rises until an equilibrium of forces is reached. Since, owing to the constant volume stream, the pressure under the support elements also rises, the bearing force of the support element on the bearing ring is very small in relation to the total force that the support element absorbs. It depends on the ratio of the bearing pocket surface area to the piston surface area of the support element. With a customary surface area ratio of about 1.1, the bearing force thus amounts to only about 10% of the support element force. Through this high transmission ratio, it is also possible to receive the force under the support element by a commercial resilient spring, e.g, a cup spring. This offers further advantages, as will be described below.
The support element preferably has a stop that can be moved parallel to the spring, which stop comes to rest on the bearing ring after a predetermined spring displacement. With this embodiment, the force-displacement characteristic of the support element can be designed individually. A linear force-displacement characteristic is obtained when the support element is seated on a spring. In contrast, if the support element is driven to its fixed position, when the stop comes to rest on the bearing ring, the change in displacement over the change in force is virtually nonexistent. Therefore, by combining these two cases, a spring characteristic can be set within wide limits.
It is also preferred for the maximum spring displacement to be shorter than the maximum lift of the support element. In this case, a further property can be incorporated into the force-displacement curve. A support element that can move freely produces a constant adjusting force during the displacement. Therefore, if the above-mentioned force-displacement relationships are combined with the constant force-displacement curve, it is already possible to implement three different segments in the force-displacement relationship.
The support surface preferably has at least one tapered approach edge. This sloped edge creates a hydrodynamic xe2x80x9ccarrying zone.xe2x80x9d This leads to improved emergency running properties and lower energy consumption.
A force device is preferably arranged between the carrier and the bearing ring, to acts in the radial direction in a press plane. It is thus possible to apply additional forces to the roll jacket in the bearing area as well. In this case, the great advantage of the seating of the roll jacket on the bearing ring via the support elements is shown in that the support elements can pass along this additional force in a virtually wear-free manner.
A throttle is preferably arranged in a feed line to the pressure chamber. This has an advantageous effect on the oscillation behavior. Throttles are known per se.
Further, the present invention is directed to a process of the type mentioned at the outset which also provides that the bearing pockets are supplied with a constant volume flow of hydraulic fluid and at least one support element is driven into the bearing ring under load as far as its fixed position. A defined position is created for the corresponding support element by the fixed position. The support element is then supported directly by the bearing ring. Because the bearing pockets are supplied with a constant volume flow of hydraulic fluid, it continues to be ensured that a fluid film can be maintained between the roll jacket and the support element in this state as well. During normal operation, in which the weight of the roll jacket is received in a different manner, the support element can be drawn out again somewhat. This ensures that the roll jacket is always supported virtually free of play, even during small changes in its geometric dimensions, as may be caused by thermal influences, for example.
Here, it is preferred for the hydraulic fluid to be conducted in the support element through a capillary arrangement. Owing to the constant volume flow, a constant pressure drop is produced in the capillary arrangement, which pressure drop moves the support element into a situation of equilibrium between the bearing ring and the roll jacket. The support element is, so to speak, gripped between two cushions of fluid, i.e., the fluid film between the roll jacket and the support element, and fluid in the pressure chamber between the support element and the bearing ring. Only when the forces acting on the support element become too great is the support element driven into its fixed position on the bearing ring. However, even in this state, provision is made for the hydraulic fluid still to reach the bearing pocket arrangement through the capillary arrangement.
The effective surface of the bearing pocket arrangement is preferably made greater than the cross section surface of the support element in the bearing ring. In this manner it is guaranteed that the pressure drop can be compensated for via the capillary arrangement as far as its force is concerned.
The present invention relates to a sag (deflection) compensation roll that includes a rotatable roll jacket, a non-rotating carrier being located inside the roll jacket, and a hydraulic support element arrangement being located between the carrier and the roll jacket. A bearing ring is located at each end of the roll jacket, the bearing rings are movable relative to the carrier in a press plane, and a bearing arrangement is located between the bearing rings and the roll jacket. The bearing arrangement includes at least three support elements distributed in a circumferential direction. At least one of the at least three support elements is movable with respect to the bearing ring.
In accordance with a feature of the present invention, the at least three support elements may include at least three hydrostatic support elements.
According to another feature of the invention, the at least one movable support element can include a bearing pocket arrangement having an effective surface which is greater than a surface of the movable support element on which a pressure acts between the bearing ring and the support element. Under load, the movable support element can be driven into the bearing ring up to a fixed position. A supply device can be arranged to deliver a constant volume flow of hydraulic fluid, and the bearing pocket arrangement may be coupled to the supply device. Further, a pressure chamber can be located between the support element and the bearing ring, and the movable support element may include a capillary arrangement positioned to couple the bearing pocket arrangement to the pressure chamber. The capillary arrangement is dimensioned so that, in an unloaded state, a predetermined initial stressing force is not exceeded, and, at a predetermined load, a predetermined minimum gap height is attained. The supply device is matched to the capillary arrangement so that, under maximum load, a minimum gap in the range of between about 20-30 xcexcm can be formed between the support element and the roll jacket.
In accordance with still another feature of the present invention, the at least one movable support element has a lift height with respect to the bearing ring in a radial direction which corresponds to a maximum change resulting from thermal differences in one of (a) at one of least one of diameter ad roll jacket and (b) carrier deformations arising from nip loads. The lift height can be in a range of between about 0.1-0.5 mm, and preferably in a range of between about 0.1-0.3 mm.
According to a further feature of the instant invention, at least one of the at least three support elements can have a curved floor on an underside positioned to face the carrier.
At least one of the at least three support elements maybe arranged in a cylinder housing having a concave curved floor which is supported on a correspondingly curved convex surface a side of the carrier.
Moreover, the support elements at one end of the roll may include a curved support surface arranged to lie against a similarly curved bearing surface on an inner side of the roll jacket. The curved support surface may be curved along a circular line which results in a radial section.
According to another feature of the invention, one of the bearing rungs can be axially positioned against the roll jacket via hydrostatic slip surfaces.
In accordance with a still further feature of the present invention, the bearing rings may be arranged on end sections of the carrier, and the end sections may have a smaller diameter than a section of the carrier axially between the end sections.
A spring may be arranged between the bearing ring and the support element. The at least one movable support element can have a stop that can be moved parallel to the spring, and the stop can come to rest against the bearing ring after a predetermined spring displacement. A maximum spring displacement can be shorter than a maximum lift of the at least one movable support element.
In accordance with another feature of the invention, a support surface of the at least one movable support element can include at least one tapered approach edge.
According to still another feature of the instant invention, a force device tan be arranged between the carrier and the bearing ring, which acts in a radially oriented press plane.
The at least one movable support element may be positioned for movement within a pressure chamber in the beating ring, and the roll can further include a throttle arranged in a line coupled to the pressure chamber.
The present invention is directed to a process for operating a sag compensation roll having a roll jacket that rotates around a carrier and that is supported in the area of its axial ends by a bearing arrangement having a bearing ring and at least three hydrostatic support elements with bearing pockets circumferentially distributed over the bearing ring. The process includes supplying the bearing pockets with a constant volume flow of hydraulic fluid, and driving at least one support element into the bearing ring under load up to the fixed position.
In accordance with yet another feature of the present invention, the process can include conducting the hydraulic fluid in the support element through a capillary arrangement. An effective surface of the beating pocket arrangement may be formed to be greater than a cross sectional surface of be support element in the bearing ring.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.